Photoactuated solid state ignition system



Jan. 14, 1969 I R. EJTARTER 7 3,421,488

PHOTOACTUATED SOLID STATE IGNITION SYSTEM Filed 001- 26, 1.964 Sheet Of 2 INVENTOR. Ralph E Tar/er llllli a, R,W

His Aflorney Jan. 14, 1969 R. E. TA TER Y 3,421,488

PHOTOACTUATED SOLID STATE IGNITION SYSTEM Filed Oct. 26, 1964 7 Sheet 2 of 2 INVENTOR. l Ralph E. Tartar His Ar/orney Fig.2

United States Patent 3,421,488 PHOTOACTUATED SOLID STATE IGNITION SYSTEM Ralph E. Tarter, Anderson, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Oct. 26, 1964, Ser. No. 406,293 US. Cl. 123-148 Int. Cl. F02p 3/ 00; F02p 23/00 7 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an ignition system for an internal combustion engine and more particularly to a semiconductor ignition system which is controlled by a photoactuated timing system.

One of the objects of this invention is to provide an ignition system for an internal combustion engine where the primary winding of an ignition coil is energized through a semiconductor that is controlled by a photoactuated timing arrangement.

Another object of this invention is to provide an ignition system for an internal combustion engine where current flow to the primary winding of an ignition coil is initiated by a first photoactuated control system and where current flow through the primary Winding is terminated by a second photoactuated control system.

Still another object of this invention is to provide an ignition system for an internal combustion engine where a semiconductor controls primary winding current and where the semiconductor is controlled by a pair of photocontrolled rectifiers.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a schematic circuit diagram of an ignition system made in accordance with this invention.

FIGURE 2 is a schematic circuit diagram of a moditied ignition system made in accordance with this invention.

Referring now to the drawings and more particularly to FIGURE 1, the reference numeral 10 designates an internal combustion engine which has a plurality of spark plugs 12 connected respectively with conductors 14 only one of which is illustrated. The conductors 14 are connected with the electrodes 16 of a distributor cap 18. A rotor 20 rotates with respect to the conductive inserts 16 and this rotor is connected with a high voltage conductor 22.

The high voltage conductor 22 is connected with the secondary winding 24 of an ignition coil generally designated by reference numeral 26. The primary winding of the ignition coil is designated by reference numeral 28.

The engine 10 is mechanically coupled to a shaft which drives slotted disks 32 and 34. The shaft 30 is 3,421,488 Patented Jan. 14, 1969 driven in synchronism with rotor contact 20 and these elements could be built into a common distributor housing. The slotted disks 32 and 34 cooperate with lamps 36 and 38 to control the amount of light applied to photo controlled rectifiers 40 and 42. The slots in the disk 32 are angularly oitset from the slots in the disk 34 so that when a slot perm-its light to impinge on the controlled rectifier 40 from the lamp 36, the disk 34 blocks light that might otherwise impinge on controlled rectifier 42 from lamp 38. In a similar fashion, when a slot of disk 34 permits light to impinge on the controlled rectifier 42, the disk 32 is in such a position as to block the light rays coming from lamp 36 which would otherwise impinge on the photocontrolled rectifier 40.

The photocontrolled rectifiers 40 and 42 each have an anode, cathode and gate. The anode of photocontrolled rectifier 40 is connected with junction 44 while the gate of controlled rectifier 40 is connected with conductor 46 through a resistor 48. The cathode of the controlled rectifier 40 is connected vw'th junction 50 and this junction is connected to ground through a resistor 52.

The photocontrolled rectifier 40 will be conductive between its anode and cathode electrodes whenever light energy impinges upon the sensitive portion of this controlled rectifier. When no light is applied to the controlled rectifier 40, it will turn oiT in its anode-cathode circuit.

The photocontrolled rectifier 42 is of the same type as the controlled rectifier 40 and has an anode connected with junction 54. The cathode of controlled rectifier 42 is connected to ground whereas the gate of the controlled rectifier 42 is connected with grounded conductor through a resistor 57a.

The photocontrolled rectifiers 40 and 42 \may be termed light sensitive switches since they are gated conductive or to a low impedance condition when light energy is applied to them.

The junction 44 is connected with a power lead 56 through resistor 57. The junction 54 is connected with power conductor 56 through resistor 59. The power conductor 56 will be connected with one side of a source of direct current 58 whenever the switch 60 is closed. The opposite side of the source of direct current 58 is connected with the grounded conductor 55. When the switch 60 is closed, both lamps 36 and 38 will be energized through resistor 62 and a grounded conductor 64. The junctions 44 and 54 are connected by a capacitor 66.

Current fiow through the rimary winding 28 of the ignition coil is controlled by a switching device which takes the form of an NPN transistor 68. The collector of transistor 68- is connected with one side of primary winding 28 While the emitter of transistor 68 is connected with junction 70. The junction 70 is grounded and is also connected to one side of the secondary winding 24 of the ignition coil. A resistor 72 is connected between junctions 70 and 74 and is connected across the base and emitter of transistor 68.

The junction 74 is connected with the emitter of another NPN transistor 76. The collector of transistor 76 is connected with power line 56 by a resistor 78. A resistor 80 is connected between junction 82 and the primary 28 of ignition coil 26. The base of transistor 76 is connected with conductor 46 and therefore is connected with junction 50.

When switch 60 is closed, the ignition system of this invention is energized and if the shaft 30 is rotated as when the engine is cranked or when the engine is running,

the transistor 68 will be switched on and off to control current flow through the primary 28. In one position of the shaft 30, the light emitted from lamp 36 will shine through a slot in disk 32 and will strike the lens of the photocontrolled rectifier 40. When this happens, the photocontrolled rectifier 40 will be turned on in its anodecathode circuit and current will flow from conductor 56, through resistor 59 and through capacitor 66. The capacitor 66 will be charged to a polarity illustrated on FIG- URE 1 and the junction 54 will be positive with respect to junction 44. Current can also flow through resistor 57, through the anode-cathode circuit of photocontrol ed rectifier 40, and through resistor 52 to ground. The voltage drop developed across resistor 52 will bias the transistor 76 to a conductive condition and current therefore will fiow through resistor 78 and through resistor 72 to ground. This supplies base current to the transistor 68 which is then biased to a conductive condition and primary winding current now can flow from junction 82, through current limiting resistor 80, through primary winding 28 and through the collector to emitter circuit of transistor 68 to ground.

With transistor 68 conductive, primary winding current fiows through the primary winding 28 to build up energy for a subsequent firing of one of the spark plugs.

As the shaft 30 continues to rotate, it moves to a position where the light emitted from lamp 38 shines through a slot in disk 34 and strikes the lens of photocontrolled rectifier 42 causing this controlled rectifier to turn on its anode-cathode circuit. Since junction 44 is more negative than junction 54 due to the charge on capacitor 66 and since junction 54 will now be substantially at ground potential, the anode of con-trolled rectifier 40 will be driven negative with respect to its cathode which causes the controlled rectifier 40 to turn off in its anode-cathode circuit. Current can now flow from conductor 56, through resistor 59 and through the anode-cathode circuit of controlled rectifier 42 to ground. Current can also fiow from power line 56, through resistor 57 and through capacitor 66 charging the capacitor to a polarity which is opposite to that shown in FIGURE 1.

When the controlled rectifier 40 is turned ofi, the base current for transistor 76 is interrupted which causes both transistors 76 and 68 to turn ofif. This interrupts current flow through the primary winding 28 causing a high voltage to be induced in the secondary winding 24 which is applied to one of the spark plugs through the rotor 20, one of the distributor insert contacts 16, and through a conductor 14.

The resistors 48 and 57a provide a bias for the photocontrolled rectifiers 40 and 42 to improve stability. These resistors also decrease the sensitivity of the photocontrolled rectifiers so that they will not be actuated by ambient light. The resistors 52 and 72 provide stability for transistors 76 and 68.

If the current gain of transistor 68 is high enough, transistor 76, resistors 78 and 72 may be omitted and junction 50 can be connected directly to junction 74 so that photo controlled rectifier 40 can drive transistor 68 directly.

It will be appreciated that the making of the primary circuit is controlled by the disk 32 whereas the breaking of the primary circuit is controlled by disk 34. The amount of time that the primary winding is energized will depend upon the angular displacement between the slots in disks 32 and 34. It is contemplated that the disk 34 could be connected with the shaft 30 through a centrifugal mechanism so that some timing adjustment could take place in response to speed of rotation of the shaft 30.

Referring now to FIGURE 2, a modified ignition system is illustrated which also employs photoactuated controlled rectifiers. In FIGURE 2, a pair of disks 84 and 86 are driven by a common shaft 90. The shaft 90 is driven by the internal combustion engine and the disks 84 and 86 are slotted in the same manner as disks 32 and 34 in FIGURE 1 and are angularly displaced in the same manner. The disk 84 controls light emitting from a lamp 92 Which strikes the lens of the photocontrolled rectifier 94. In a similar fashion, the light emitted fr lamp 96 can strike the lens of the photocontrolled rectifier 98 at periodic intervals determined by the slot configuration of disk 86.

The ignition system of FIGURE 2 is powered by a source of direct current 100 which can be a storage battery on a motor vehicle. The negative side of the direct current source is directly connected with conductor 102 which is grounded. The positive side of the source of direct current is directly connected with conductor 104. A switch 106 is provided which can connect conductor 104 directly with conductor 108 or can connect conductors 104 or 108 through resistor 110. The direct connection between conductor 104 and 108 is used when the engine is being cranked.

The photocontrolled rectifiers are connected between conductor 108 and ground through a circuit that includes resistor 112, and junction 114.

Current flow through the primary winding 28 of the ignition coil is controlled by a switching device which, in this embodiment, takes the form of a gate controlled switch having an anode 116, a cathode 11:8 and a gate 120. The gate controlled switch or semiconductor switch is of a type that is turned on when the gate is positive with respect to the cathode and is turned off when the potential of the gate is lower than the potential of the cathode regardless of anode potential. This device therefore provides on-otf control by varying the potential of the gate as distinguished from conventional controlled rectifiers where the device can only be turned off where the cathode is at a higher potential than the anode.

The anode 116 of gate controlled switch 115 is connected to one side of the primary winding 28. The opposite side of the primary winding is connected with conductor 108. The cathode 118 of controlled rectifier 115 is grounded through a resistor 122. It is seen that one side of the secondary winding 24 of the ignition coil 26 is connected with grounded junction 124.

The gate 120 of gate controlled switch 115 is connected with junction 126. A resistor 128 connects the junctions 124 and 126. A capacitor 130 and resistor 132 are connected in series between junctions 114 and 126.

The lamps 92 and 96 are energized through conductor 134 and resistor 136 whenever the switch 106 is in one of its closed positions.

When the shaft 90 is driven by the engine as when the engine is being cranked or when the engine is running, light energy is sequentially applied to the photocontrolled rectifiers 94 and 98. When light shines through a slot in disk 84 and strikes the lens of photocontrolled rectifier 94, this controlled rectifier will turn on in its anodecathode circuit. This will allow current to flow from the positive side of the battery 100, through conductor 104, through conductor 108, through current limiting resistor 112, through the anode-cathode circuit of controlled rectifier 94, through capacitor 130, through resistor 132, through resistor 128, and through the gate to cathode circuit of gate controlled switch 115. This supplies a forward bias to the gate controlled switch 115 causing it to turn on its anode-cathode circuit. Because of this, current can flow through the primary winding 28 from the direct current source 100 since the gate controlled switch 115 is now turned on.

As the capacitor 130 becomes charged when photocontrolled rectifier 94 was turned on, the anode to cathode current through controlled rectifier 94 will decrease and eventually will drop to a point where the photocontrolled rectifier 94 will turn off.

As the shaft 90 continues to rotate, the time will come when light will shine through one of the slots of a disk 86 from lamp 96 and therefore will strike the lens of the photocontrolled rectifier 98 turning this controlled rectifier on in its anode-cathode circuit. The capacitor 130 will now discharge through the anode-cathode circuit of photocontrolled rectifier 98 and through the cathode-gate circuit of the gate controlled switch 115. This will cause the gate controlled switch 15 to turn off in its anodecathode circuit to therefore break the circuit for the primary winding 28. When this happens, a high voltage is induced in the secondary winding 24 which is applied to one of the spark plugs through rotor contact 20.

The photocontrolled rectifier 98 will turn ofi when capacitor 130 has discharged sufficiently so that the current from its anode to its cathode drops below the required holding current.

The photo controlled rectifiers are provided with resistors 144 and 146 to provide a bias for these devices and to decrease sensitivity in order that the photo controlled rectifiers 94 and 98 will not be actuated or turned on by ambient light and will be more stable with respect to light actuation over a wide temperature range.

While the embodiments of the present invention as herein disclosed constitute a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. An ignition system for an internal combustion engine comprising, a source of direct current, a gate controlled switch having an anode, cathode and gate, said gate controlled switch being of a type that is turned on in its anode-cathode circuit when the potential of its gate exceeds the potential of its cathode and turned off in its anode-cathode circuit by the application of a potential to its cathode and turned off in its anode-cathode circuit by the application of a potential to its cathode-gate circuit which lowers the potential of its gate relative to its cathode, an ignition coil having a primary winding and a secondary winding, means connecting said primary winding and the anode and cathode of said gate controlled switch across said source of direct current, first and second photoactuated switching devices which are biased conductive when light energy is applied thereto, means for applying light energy sequentially to said photoactuated switching devices in synchronism with operation of said engine, a capacitor, a charging circuit for said capacitor including in a series connection said first photoactuated switching device and the gate and cathode circuit of said gate controlled switch, and a discharging circuit for said capacitor including in a series connection said second photoactuated switching device and the cathode-gate circuit of said gate controlled switch.

2. The ignition system according to claim 1 where the photoactuated switches are photocontrolled rectifiers.

3. An ignition system for an internal combustion engine comprising, a source of direct current having positive and negative terminals, an ignition coil having a primary winding and a secondary winding, a switching device having a pair of current carrying terminals and a control terminal, means connecting said current carrying terminals of said switching device and said primary winding in series across said source of direct current, a photocontrolled rectifier having an anode and a cathode, means connecting the anode-cathode circuit of said photocontrolled rectifier across said source of direct current with the anode connected to said positive terminal and said cathode connected to said negative terminal, means connecting the cathode of said photocontrolled rectifier with the control terminal of said switching device, the cathode of said photocontrolled rectifier providing a potential at the control terminal of said switching device which is operative to bias said switching device conductive when said photocontrolled rectifier is gated conductive by the application of light energy thereto, the potential applied to said control terminal of said switching device being of such a value as to bias said switching device nonconductive when said photocontrolled rectifier is nonconductive, a source of light, a timing shaft driven in synchronism with said engine, a first control means located between said source of light and said photocontrolled rectifier and arranged to permit the periodic application of light energy to said photocontrolled rectifier at first angularly spaced positions of said timing shaft, said photocontrolled rectifier biased conductive when light is applied to it and remaining conductive by the forward bias of said direct current source until its anode-cathode circuit is reverse biased, and means for periodically reverse biasing the anode-cathode circuit of said photocontrolled rectifier when said timing shaft reaches second angularly spaced positions spaced from said first angularly spaced positions of said timing shaft, said last named means including a capacitor, a circuit connecting said capacitor across said source of direct current including the anode-cathode circuit of said photocontrolled rectifier whereby said capacitor is charged when said photocontrolled rectifier is gated conductive, a light sensitive switch which is switched conductive when light is applied thereto, means connecting said capacitor, said light sensitive switch and the cathode-anode circuit of said photocontrolled rectifier in a series loop circuit whereby said capacitor discharges through said light sensitive switch and reverse biases said photo controlled rectifier when light is applied to said light sensitive switch, a second control means mechanically coupled to said timing shaft and positioned between said source of light and said light sensitive switch, said second control means permitting the application of light energy to light sensitive switch at said second angularly spaced positions of said timing shaft whereby said photocontrolled rectifier and said semiconductor switch are biased nonconductive at said second angularly spaced positions of said timing shaft.

4. An electrical circuit for energizing and deenergizing an electrical load in response to and in synchronism with the movement of a movable device com prising, a source of direct current, a gate controlled switch having an anode, cathode and gate, said gate controlled switch being of a type that is turned on in its anode-cathode circuit when the potential of its gate exceeds the potential of its cathode and which is turned off in its anode-cathode circuit by the application of a potential to its cathode-gate circuit which lowers the potential of its gate relative to its cathode, means connecting said gate controlled switch with an electrical load, a movable device, first and second photoactuated switched which are switched conductive by the application of light energy thereto, means for applying light energy sequentially to said first and second photo-actuated switches in a predetermined sequence and in synchronism with movement of said movable device, a capacitor, a charging circuit for said capacitor connected across said source of direct current and including in a series connection said first photoactuated switch and the gate-cathode circuit of said gate controlled switch, said charging circuit operative to bias said gate controlled switch conductive in its anodecathode circuit when said first photo actuated switch is conductive, and a circuit for discharging said capacitor and to thereby turn off said gate controlled switch in its anode-cathode circuit by reducing the voltage of its gate relative to its cathode, said circuit including in a series connection said second photo actuated switch and the cathode-gate circuit of said gate controlled switch.

5. An ignition system for an internal combustion engine comprising, a source of direct current, an ignition coil having a primary winding and a secondary winding, a gate controlled switch having a gate, anode and cathode, said gate controlled switch being of a type that can be turned on when its gate has a higher potential than its cathode and turned off when its cathode potential exceeds its gate potential, means connecting said primary winding and the anode-cathode circuit of said gate controlled switch in series across said source of direct current, first and second photocontrolled rectifiers which are gated conductive by the application of light energy thereto, means connecting the anode-cathode circuits of said first and second photo-controlled rectifiers in series with each other and across said source of direct current, a junction on the circuit that connects the cathode of said first photocontrolled rectifier with the anode of the second photocontrolled rectifier, a capacitor connected between said junction and the gate of said gate controlled switch, a source of light, a shaft mechanically coupled to said engine and driven thereby, and first and second slotted control members positioned respectively between said source of light and said first and second photocontrolled rectifiers, said control members being so oriented with respect to said shaft that light energy is sequentially applied to said first and second photo controlled rectifiers at time spaced periods corresponding to different angular positions of said shaft, said gate controlled switch biased conductive when said first photocontrolled rectifier is gated conductive through the circuit connecting said junction and the gate of said gate controlled switch, said gate controlled switch biased nonconductive when light energy is applied to said second photocontrolled rectifier to provide a discharge path for said capacitor and a reverse bias on said gate controlled switch.

6. An ignition system for an internal combustion engine comprising, a source of direct current, an ignition coil having a primary winding and a secondary winding, a transistor having an emitter, collector and base, means connecting said primary winding and the emitter-collector circuit of said transistor in series across said source of direct current, a first photo controlled rectifier, a circuit connected across said source of direct current including the anode-cathode circuit of said first photocontrolled rectifier, a point on said circuit having a potential which varies between maximum and minimum values depending upon whether or not said first photo controlled rectifier is conductive or nonconductive, means coupling the base of said transistor to said point on said circuit whereby the potential of said base varies as a function of the conduction or nonconduction of said first photocontrolled rectifier, a second photocontrolled rectifier connected across said source of direct current, a capacitor connecting the anodes of said first and second photocontrolled rectifiers,

that light energy is sequentially applied to said first and second photocontrolled rectifiers at time spaced periods corresponding to different angular positions of said shaft, whereby said primary winding is alternately energized and deenergized by the sequential application of light energy to said first and second photocontrolled rectifiers.

7. The electric circuit according to claim 3 Where the first and second photoactuated switches are photocontrolled rectifiers.

References Cited UNITED STATES PATENTS 2,402,719 6/ 1946 Allison 250233 X 2,791,724 5/1957 Ekblom et a1 250-209 3,235,742 2/1966 Peters 250233 3,242,420 3/1966 Ulrey 30788.5 X 3,331,362 7/1967 Mitchell 307-885 X 3,354,312 11/1967 Howell.

OTHER REFERENCES Howell, E. K.: Light Activated Switch Expands Uses of Silicon-Controlled Rectifiers, Electronics magazine, vol. 37, No. 15, May 4, 1964.

LAURENCE M. GOODRIDGE, Primary Examiner.

US. Cl. X.R. 

